* Jianjun Duan (du...@linux.vnet.ibm.com) wrote:
> Currently we cannot directly transfer a QTAILQ instance because of the
> limitation in the migration code. Here we introduce an approach to
> transfer such structures. We created VMStateInfo vmstate_info_qtailq
> for QTAILQ. Similar VMStateInfo can be created for other data structures
> such as list.
>
> When a QTAILQ is migrated from source to target, it is appended to the
> corresponding QTAILQ structure, which is assumed to have been properly
> initialized.
>
> This approach will be used to transfer pending_events and ccs_list in spapr
> state.
>
> We also create some macros in qemu/queue.h to access a QTAILQ using pointer
> arithmetic. This ensures that we do not depend on the implementation
> details about QTAILQ in the migration code.
>
> Signed-off-by: Jianjun Duan <du...@linux.vnet.ibm.com>
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> include/migration/vmstate.h | 20 +++++++++++++
> include/qemu/queue.h | 60 +++++++++++++++++++++++++++++++++++++++
> migration/trace-events | 4 +++
> migration/vmstate.c | 69
> +++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 153 insertions(+)
>
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index eafc8f2..e47ad6e 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -253,6 +253,7 @@ extern const VMStateInfo vmstate_info_timer;
> extern const VMStateInfo vmstate_info_buffer;
> extern const VMStateInfo vmstate_info_unused_buffer;
> extern const VMStateInfo vmstate_info_bitmap;
> +extern const VMStateInfo vmstate_info_qtailq;
>
> #define type_check_2darray(t1,t2,n,m) ((t1(*)[n][m])0 - (t2*)0)
> #define type_check_array(t1,t2,n) ((t1(*)[n])0 - (t2*)0)
> @@ -664,6 +665,25 @@ extern const VMStateInfo vmstate_info_bitmap;
> .offset = offsetof(_state, _field), \
> }
>
> +/* For migrating a QTAILQ.
> + * Target QTAILQ needs be properly initialized.
> + * _type: type of QTAILQ element
> + * _next: name of QTAILQ entry field in QTAILQ element
> + * _vmsd: VMSD for QTAILQ element
> + * size: size of QTAILQ element
> + * start: offset of QTAILQ entry in QTAILQ element
> + */
> +#define VMSTATE_QTAILQ_V(_field, _state, _version, _vmsd, _type, _next) \
> +{ \
> + .name = (stringify(_field)), \
> + .version_id = (_version), \
> + .vmsd = &(_vmsd), \
> + .size = sizeof(_type), \
> + .info = &vmstate_info_qtailq, \
> + .offset = offsetof(_state, _field), \
> + .start = offsetof(_type, _next), \
> +}
> +
> /* _f : field name
> _f_n : num of elements field_name
> _n : num of elements
> diff --git a/include/qemu/queue.h b/include/qemu/queue.h
> index 342073f..35292c3 100644
> --- a/include/qemu/queue.h
> +++ b/include/qemu/queue.h
> @@ -438,4 +438,64 @@ struct {
> \
> #define QTAILQ_PREV(elm, headname, field) \
> (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
>
> +#define field_at_offset(base, offset, type)
> \
> + ((type) (((char *) (base)) + (offset)))
> +
> +typedef struct DUMMY_Q_ENTRY DUMMY_Q_ENTRY;
> +typedef struct DUMMY_Q DUMMY_Q;
> +
> +struct DUMMY_Q_ENTRY {
> + QTAILQ_ENTRY(DUMMY_Q_ENTRY) next;
> +};
> +
> +struct DUMMY_Q {
> + QTAILQ_HEAD(DUMMY_Q_HEAD, DUMMY_Q_ENTRY) head;
> +};
> +
> +#define dummy_q ((DUMMY_Q *) 0)
> +#define dummy_qe ((DUMMY_Q_ENTRY *) 0)
> +
> +/*
> + * Offsets of layout of a tail queue head.
> + */
> +#define QTAILQ_FIRST_OFFSET (offsetof(typeof(dummy_q->head), tqh_first))
> +#define QTAILQ_LAST_OFFSET (offsetof(typeof(dummy_q->head), tqh_last))
> +/*
> + * Raw access of elements of a tail queue
> + */
> +#define QTAILQ_RAW_FIRST(head)
> \
> + (*field_at_offset(head, QTAILQ_FIRST_OFFSET, void **))
> +#define QTAILQ_RAW_TQH_LAST(head)
> \
> + (*field_at_offset(head, QTAILQ_LAST_OFFSET, void ***))
> +
> +/*
> + * Offsets of layout of a tail queue element.
> + */
> +#define QTAILQ_NEXT_OFFSET (offsetof(typeof(dummy_qe->next), tqe_next))
> +#define QTAILQ_PREV_OFFSET (offsetof(typeof(dummy_qe->next), tqe_prev))
> +
> +/*
> + * Raw access of elements of a tail entry
> + */
> +#define QTAILQ_RAW_NEXT(elm, entry)
> \
> + (*field_at_offset(elm, entry + QTAILQ_NEXT_OFFSET, void **))
> +#define QTAILQ_RAW_TQE_PREV(elm, entry)
> \
> + (*field_at_offset(elm, entry + QTAILQ_PREV_OFFSET, void ***))
> +/*
> + * Tail queue tranversal using pointer arithmetic.
> + */
> +#define QTAILQ_RAW_FOREACH(elm, head, entry)
> \
> + for ((elm) = QTAILQ_RAW_FIRST(head);
> \
> + (elm);
> \
> + (elm) = QTAILQ_RAW_NEXT(elm, entry))
> +/*
> + * Tail queue insertion using pointer arithmetic.
> + */
> +#define QTAILQ_RAW_INSERT_TAIL(head, elm, entry) do {
> \
> + QTAILQ_RAW_NEXT(elm, entry) = NULL;
> \
> + QTAILQ_RAW_TQE_PREV(elm, entry) = QTAILQ_RAW_TQH_LAST(head);
> \
> + *QTAILQ_RAW_TQH_LAST(head) = (elm);
> \
> + QTAILQ_RAW_TQH_LAST(head) = &QTAILQ_RAW_NEXT(elm, entry);
> \
> +} while (/*CONSTCOND*/0)
> +
> #endif /* QEMU_SYS_QUEUE_H */
> diff --git a/migration/trace-events b/migration/trace-events
> index 94134f7..c46f9e9 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -52,6 +52,10 @@ vmstate_n_elems(const char *name, int n_elems) "%s: %d"
> vmstate_subsection_load(const char *parent) "%s"
> vmstate_subsection_load_bad(const char *parent, const char *sub, const char
> *sub2) "%s: %s/%s"
> vmstate_subsection_load_good(const char *parent) "%s"
> +get_qtailq(const char *name, int version_id) "%s v%d"
> +get_qtailq_end(const char *name, const char *reason, int val) "%s %s/%d"
> +put_qtailq(const char *name, int version_id) "%s v%d"
> +put_qtailq_end(const char *name, const char *reason) "%s %s"
>
> # migration/qemu-file.c
> qemu_file_fclose(void) ""
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index 7b4bd6e..2f9d4ba 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -5,6 +5,7 @@
> #include "migration/vmstate.h"
> #include "qemu/bitops.h"
> #include "qemu/error-report.h"
> +#include "qemu/queue.h"
> #include "trace.h"
> #include "migration/qjson.h"
>
> @@ -965,3 +966,71 @@ const VMStateInfo vmstate_info_bitmap = {
> .get = get_bitmap,
> .put = put_bitmap,
> };
> +
> +/* get for QTAILQ
> + * meta data about the QTAILQ is encoded in a VMStateField structure
> + */
> +static int get_qtailq(QEMUFile *f, void *pv, size_t unused_size,
> + VMStateField *field)
> +{
> + int ret = 0;
> + const VMStateDescription *vmsd = field->vmsd;
> + /* size of a QTAILQ element */
> + size_t size = field->size;
> + /* offset of the QTAILQ entry in a QTAILQ element */
> + size_t entry_offset = field->start;
> + int version_id = field->version_id;
> + void *elm;
> +
> + trace_get_qtailq(vmsd->name, version_id);
> + if (version_id > vmsd->version_id) {
> + error_report("%s %s", vmsd->name, "too new");
> + trace_get_qtailq_end(vmsd->name, "too new", -EINVAL);
> +
> + return -EINVAL;
> + }
> + if (version_id < vmsd->minimum_version_id) {
> + error_report("%s %s", vmsd->name, "too old");
> + trace_get_qtailq_end(vmsd->name, "too old", -EINVAL);
> + return -EINVAL;
> + }
> +
> + while (qemu_get_byte(f)) {
> + elm = g_malloc(size);
> + ret = vmstate_load_state(f, vmsd, elm, version_id);
> + if (ret) {
> + return ret;
> + }
> + QTAILQ_RAW_INSERT_TAIL(pv, elm, entry_offset);
> + }
> +
> + trace_get_qtailq_end(vmsd->name, "end", ret);
> + return ret;
> +}
> +
> +/* put for QTAILQ */
> +static int put_qtailq(QEMUFile *f, void *pv, size_t unused_size,
> + VMStateField *field, QJSON *vmdesc)
> +{
> + const VMStateDescription *vmsd = field->vmsd;
> + /* offset of the QTAILQ entry in a QTAILQ element*/
> + size_t entry_offset = field->start;
> + void *elm;
> +
> + trace_put_qtailq(vmsd->name, vmsd->version_id);
> +
> + QTAILQ_RAW_FOREACH(elm, pv, entry_offset) {
> + qemu_put_byte(f, true);
> + vmstate_save_state(f, vmsd, elm, vmdesc);
> + }
> + qemu_put_byte(f, false);
> +
> + trace_put_qtailq_end(vmsd->name, "end");
> +
> + return 0;
> +}
> +const VMStateInfo vmstate_info_qtailq = {
> + .name = "qtailq",
> + .get = get_qtailq,
> + .put = put_qtailq,
> +};
> --
> 1.9.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
